Toxicity to Rhinella arenarum tadpoles (Anura, Bufonidae) of herbicide mixtures commonly used to treat fallow containing resistant weeds: glyphosate–dicamba and glyphosate–flurochloridone. (April 2020)

• Record Type: Journal Article
• Authors: Ruiz de Arcaute, Celeste; Brodeur, Julie C.; Soloneski, Sonia; Larramendy, Marcelo L.
• Is Part Of: Chemosphere. Volume 245(2020)
• Publication Date: 2020-04
• Subjects: Agrochemical mixtures -- Amphibians -- Dicamba-based herbicide formulation -- Flurochloridone-based herbicide formulation -- Glyphosate-based herbicide formulation -- Contamination; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.125623
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Glyphosate (GLY)-dicamba (DIC) and GLY-flurochloridone (FLC) are herbicide mixtures which are widely used for treating fallow containing glyphosate resistant weeds. The aim of this study was to evaluate the acute toxic effects and the prevailing interactions on stage 36 tadpoles of the anuran species Rhinella arenarum when exposed to equitoxic and non-equitoxic combinations of these herbicide combinations. Experiments were realized using the following combinations of commercial formulations: 48% GLY-based Credit® + 57.71% DIC-based Banvel® and 48% GLY-based Credit® + 25% FLC-based Twin Pack Gold®. GLY-DIC and GLY-FLC equitoxic mixtures were assayed mixing each constituent with an equivalent individual toxicity able to induce the same lethality effect. After 96 h of exposure, GLY-DIC and GLY-FLC equitoxic mixtures presented toxic unit 50 values (TU50 96h ) of 1.74 (confidence interval: 1.58–1.92) and 1.54 (confidence interval: 1.46–1.62) respectively, indicating the presence of a weak antagonistic interaction as TU values were greater than 1. For their part, most non-equitoxic combinations of GLY-DIC and GLY-FLC tested did not significantly differ from additivity, the only exception being when DIC and FLC were fixed at 0.33 TUs, where a weak antagonism was observed. Overall, results indicate that the toxicity of both GLY-DIC and GLY-FLC mixtures to R. arenarum tadpoles vary from additive to slightly antagonistic, depending on the proportion of constituting herbicide formulations present in the mixture. Graphical abstract: Image 1 Highlights: GLY-DIC and GLY-FLC mixtures induced-lethality on Rhinella arenarum tadpoles. Determination of the toxic unit (=LC50 96 h) was employed as lethal end point. Equitoxic mixtures indicated weak antagonistic interaction of the herbicides. Non-equitoxic mixtures varied from additive to slightly antagonistic interaction. Toxicity depends upon the proportion of each constituting herbicide formulation.